Thanks again for your views Chris - you obviously know a lot about this stuff.
I'm assuming that the spekers will be changed for ones of the same impedance, but bigger diameter - if that's the case, surely the amp will not have any problems?
On my GS300-2, I've actually looked at the speakers, and they do seem to be 4inch. They're mounted in pods and there seems to be plently of room in there if the pods are removed - I think I've read that you can get 6inch speakers in there.
There is a Nakamichi upgrade for the GS3 - perhaps the demo you saw had that fitted, with bigger speakers??
Are you absolutely sure that stock speakers on the stock Pioneer amp on a GS3-2 are 2ohm??? - if that's true - then I agree there may be a problem?
The reason I want to upgrade is that the 4inch speakers sound faily flat and distort at high volumes. I'm looking for a fuller, brighter sound, which I'm hoping I'm going to get from 6inch cones.
Cheers mate
Rod